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Stihl Ms 180c Oil feed Chewed worm drive

Discussion in 'Tools and Materials' started by stevehicks, 5 Jun 2012.

  1. stevehicks

    stevehicks

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    Hi, ive stripped my saw many a time, and have found that the saw just chews up the thread on the worm drive. Is this a pump problem, as the the pipes are clear. The worm has been changed 3 times now :(((

    Please Help
     
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  3. Burnerman

    Burnerman

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    Steve, the worm drive is spun by a wire which locates into the clutch drum.....this is so oil is only delivered when the chain is revolving.
    The plastic worm should be free to revolve on the crankshaft, and the tiny gear teeth of the oil pump are driven by this.
    There shouldn't be much end play on the worm, when the clutch drum is in place.
    If the worm is stripping, maybe the pump is seized (very rare)? You should be easily able to turn the pump gear by hand.
    John :)
     
  4. stevehicks

    stevehicks

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    Thanks Burnerman,

    it was a while ago when I last stripped it, and was sure that the pump was free- could of been wrong. The saw has been in the back of the shed for a while, but as i'm having problems with my older saw, thought it was time to look at it again!

    I wondered if anyone had encountered similar stripping problems before I dismember the saw AGAIN :(
     
  5. Burnerman

    Burnerman

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    I'm wondering if there is a shim missing from behind the clutch drum.....as you realise, the clutch has a left hand thread and as it tightens maybe its locking the worm gear up.
    This isn't a common fault, but blocking of the oil pump is! The pump, incidentally is just a small cylindrical thing about 30mm long, with a toothed gear on one end - its quite awkward to remove.
    John :)
     
  6. stevehicks

    stevehicks

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    Hi John,
    I stripped her last night, the shim is there, and it's chewed up my worm again :(
    The pump gear wheel spins freely. ...

    Any ideas?

    Steve
     
  7. Burnerman

    Burnerman

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    Just thinking about this one Steve.....
    I reckon the only way the worm gear can strip is because its moving out of alignment with the pump gear its meant to be driving - in other words its sliding along the crankshaft, for reasons unknown.
    I think its time, when you get a new worm, to compare your machine with a diagram that the Stihl parts people have - perhaps there's a shim adrift or its in the wrong place or something.
    Thats all I can think of really - unfortunately I don't have an 018 saw in at present, or I'd have a closer look.
    John :)
     
  8. stevehicks

    stevehicks

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    Hi,
    I think I've managed to upload a photo:-/
     
  9. Burnerman

    Burnerman

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    I have to say, all looks pretty kosher there Steve.
    A few probably obvious things:
    Is there much end play on the crankshaft?
    Is there any up and down play on the main bearings?
    Does the worm slide snugly onto the crankshaft without binding?
    Have you moved the oil pump i.e could it be meshing tighter with the worm than before?
    Do you engage the worm wire onto the clutch drum every time?

    I've never had it before, but I wonder if the pump is locking up somehow - this would strip the worm immediately.
    John :)
     
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  11. trialscot

    trialscot

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    Funny, I can't see a photo!.
    If this model does have a wire driving the worm, there is a tiny cut out in the edge of the clutch drum that the wire must engage into. If it doesn't, I suppose it could jam the worm.
     
  12. stevehicks

    stevehicks

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    Hi all,

    The drive wire is always located into sprocket.

    @ John,
    No play, the saw not done that much work-related it's either the 2nd or 3rd sprocket fitted with very little wear in this one:*)
    The saw was never stripped right down until the first worm was stripped. ...???
     
  13. Burnerman

    Burnerman

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    Right Steve, the only thing I can suggest at the moment is for you to engage a new worm, push it right on to the crankshaft, and you spin it by hand, feeling for tight spots.
    As I've said before, worm gears strip due to misalignment, seizure of the pinion (oil pump in this case) or lack of lubrication.
    Can you pull the pump gear down a bit with a small screwdriver? That shouldn't be possible.
    John :)
     
  14. stevehicks

    stevehicks

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    Hey John,

    I can spin the pump cog with a terminal driver...... this is free to turn, and doesn't feel like any tight spots are there.

    Did you mean is there any movement in the cog gear- as in up and down from where it should be fixed? :confused:
     
  15. Burnerman

    Burnerman

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    I don't suspect any problem with the pump Steve, but the drive gear shouldn't have any up or down movement at all.
    By the way, GHS sell the worm gear for less than a fiver (plus postage). Brilliant firm.
    John :)
     
  16. stevehicks

    stevehicks

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    Ill check for movement shortly, in between the showers :mad:

    GHS? whats the best way to get in touch, as google search comes up as something High School.

    Steve
     
  17. Burnerman

    Burnerman

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    ebay mate - Garden Hire Spares ;)
    Loads of pattern bits for many machines, and I've never bought a dud part yet from them!
    John :)
     
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